Ignition system



Aug. 10, 1948. B. H. SHORT ETAL 2,446,671

IGNITION SYS TEM Filed May 14, 1946 INVENTOR5 15M A WwmfW BY g ATTORNg Patented Aug. 10, 1948 I IGNITION SYSTEM- Brooks H. Short and Herman L. llartzell, Anderson. Ind., assignors to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application May 14, 1946, Serial N0. 669,495

1 Claim.

i This invention relates. to ignition apparatus for internal combustion engines and particularly to application of Short and Tynan, Serial No. 611,402, filed August 18, 1945. That application discloses the supplying of energy for ignition purposes by the discharge of a condenser which is charged'by a power source, the discharge being withheld until the required instant of ignition by a thyratron under control by an ignition,timer or periodic circuit make and break device driven by the engine. In such cases, the variations in the timing of the ignition in response to variations in engine speed and engine load would be effected by the use of a timer having speed responsive means for varying angular relation between the ignition timer cam and the engine driven shaft which drives the cam and means responsive to engine intake suction for varying. the angular relation between the circuit breaker lever and the cam.

An object of the present invention is to control the thyratron by means otherthan that which requires the use of a circuit breaker. This object is accomplished in the disclosed embodiment of the invention by the use of a pick-up coil connected with a grid of the thyratron and threaded by magnetic flux produced by a permanent magnet attached to the engine flywheel or other rotating part driven by the engine. Since the voltage gencrated in the pick-up coil is a function of speed and flux, the surface of the permanent magnet which is presented as a pole piece surrounded by the pick-up coil is so shaped that the timing of the ignition can be varied according to engine speed. The pole piece is moved toward or away from the permanent magnet in response to variations in engine load as indicated by variations in engine intake suction. 6

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawing, wherein apreferred embodiment of the present invention is clearly shown.

In the drawing:

Fig. 1 is a diagram of a form of the invention.

Fig. 2 is a fragment'aryview, partly in section, on the line 2-2 of Fig. 1.

Referring to Fig. 1, numerals Ill and H are terminals connected with a current source and with wires l2 and 13 between which there is located a potentiometer or voltage divider comprising resistances l4 and I5 connected by tap l6. Wire I2 is connected through a resistance H with a condenser l8 connected with the primary apparatus such as disclosed in the copending winding I9 of an ignition coil having a secondary winding 2| connected with a distributor 22 connected with the various spark plugs 23 of the cnginc. The discharging of the condenser l8 for the purpose of supplying energy to the coil 20 for ignition purposesis under control by a thyratron 25 (preferably filled with hydrogen) whose plate 26 is connected with wire l2 whose cathode 21 is connected with wire l3. Cathode heater 28 is connected between wire I3 and tap l6.

Tube 25 is tripped by the action of a magneto generator driven by the engine. For this purpose the magneto includes a pick-up coil connectedwith the grid 29 of tube 25. Coil 30 is wound upon a spool 3| attached to the frame 32 of an engine having'a shaft 33 which drives a flywheel 34 in the direction of arrow 34a when viewed in the direction of arrow 34b. Flywheel 34 carries a permanent magnet 35 having a surface 36 of suitable contour for a purpose to be 30 sufficient to render the thyratron 25 conducting when the voltage of the pick-up coil has increased to the required value.

The voltage generated in thepick-up coil is a function of speed and flux. Therefore, in order to generate in the pick-up coil a voltage sufficient to trip the thyratron at lowest speed, the flux density at the gap between the magnet 35 and the pole face 31 must be the greatest. As speed increases the flux density may diminish. The surface 36 of the magnet is shaped to provide air gap varying with speed. At low speed, the required air gap is obtained when portion A of the magnet 35 is adjacent pole face 31. At medium speed suflicient voltage to trip the thyratron would be generated'when portion B of the mag- In order to provide for control of ignition tim-i ing in response to variations in load, the core '38 is caused to move axially by means responsive to engine intake suction. For this purpose there is provided a bracket 40 supporting a. flexible metal bellows Ii, the lower end of which is connected by pin 42 with a bell crank lever 3 pivoted at 44 upona bracket 45 integral with the bracket 40. Lever 43 has a slot 46 receiving a pin 41 carried by the pole piece 38. Within the bellows ll there is located a spring 49 tending to expand the bellows and cause the core 38 to move toward the left until a stop 38a thereof engages spool II. This establishes a maximum distance between the pole face 31 and the face 36 of magnet 35. The interior of bellows ll is connected by pipe 50 with the engine intake manifold. V

' When engine suction is relatively low, due to wide opening of the throttle for full load operation, the spring 49 will be permitted to locate the core 38 as shown. When the engine operates at partial load as when driving on a level road, the bellows 4! would be somewhat collapsed and the pole face 31 would be moved toward the right from the position shown, Consequently ignition would occur earlier than when the engine operates at full load. the speed remaining the same. At high speed and part load the timing of ignition would occur earlier than at high speed,

. full load. At low speed the timing of the ignition would be earlier at part load than at full load. At low speed and full load a greater amount of retard would be provided since the thyratron would not be tripped until part A of the magnet is adjacent the pole face 3'! of core 38.

While the embodiment of the present invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claim 35 which follows.

What is claimed is as follows:

Ignition apparatus comprising an ignition coil having a secondary winding for connection with a spark gap and having a primary winding, a condenser connected with the'primary winding and charged by a current source, means responsive to a certain voltage to provide for the discharge of the condenser at the required instant of ignition and a magneto generator having a pick-up coil providing a voltage for said means, a core surrounded by the coil and having a pole face anda permanent magnet moved by the engine past the pole face and presenting to the pole face a surface of such contour as to provide an air gap of varying width, a portion of the magnet REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,205,561 Holthouse June 25, 1940 2,338,906 Dausinger Jan. 11, 1944 2,353,527 Touceda July 11, 1944 

